hw9 initial commit. Starting with imp type checking as scaffold.
added a type assignment
concrete types are constructors of type
prepared semantics file
added basic rules
finished typed checker for simply typed lambda calculus
extended types to include generic types
Merge branch 'hw9' of github.com:cdmihai/522 into hw9
fixed bug for lambda abstraction type
-> type shold be right associative
type of cond should be bool -> t -> t -> t
added syntax for generics and semantics for polymorphic abstraction
formatting and renamings
type has to support substitution
comments
rules for polymorhic type instantiation
preconditions for type instantiation and type abstraction
deleted old code
new polymorphic example and new polymorhic conditional
removed useless code